HTTP ETag cache validators and the Core Web Vitals
83.8% of audited sites (176,769) serve ETag headers on their responses (82% good LCP, 1.5s median), while 16.2% omit ETag validators (83% good LCP, 1.4s median).
16.2% of sites have no ETag cache validation. Of the 83.8% that do, 100% use ETag validators, and 82% of those sites have a good LCP, against 82% of all sites.
LCP pass rate
Sites with ETag validators ETag cache validation have a good LCP most often: 82%, against 82% of all sites.
ETag cache validation usage
83.8% of sites use ETag cache validation, and 100% of those use ETag validators.
LCP phase breakdown for sites with and without ETag headers
Across the four LCP sub-parts in Chrome's field data, the largest gap between ETag validators and no ETag header sits in resource load delay: 327 ms median for ETag validators against 261 ms for no ETag header. Overall median field LCP is 1.5s for ETag validators (TTFB 644 ms, load delay 327 ms, load duration 144 ms, render delay 226 ms) versus 1.5s for no ETag header.
Understanding HTTP ETag cache validators
Why ETag headers matter on repeat visits and CDN edge revalidations
An Entity Tag (ETag) is an opaque version identifier attached to an HTTP response. Across 176,769 audited sites (83.8%) that emit ETag headers, browsers and CDN edges can send If-None-Match conditional requests when cached files expire and receive a header-only 304 Not Modified response instead of re-downloading the full payload. Because first-visit crawl and field LCP measurements weight initial loads and immutable hashed assets heavily, sites with ETag headers record 82% good LCP (1.5s median, 644 ms TTFB) while the 16.2% without ETag headers record 83% good LCP (1.4s median, 664 ms TTFB).
Enable strong or weak content-based ETag headers on your web server or CDN edge so expired cache entries can revalidate via If-None-Match and 304 Not Modified in a single header-only round trip. If you run multiple origin servers behind a load balancer, avoid inode-based default ETags in Apache or nginx so revalidation requests never miss across nodes. Across all audited sites, 83.8% emit ETag validators (82% good LCP, 1.5s median) and 16.2% omit them (83% good LCP, 1.4s median).
How ETag cache validation plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 65,509 sites 87.7% of WordPress sites emit ETag headers, while 12.3% omit them.
Across WordPress sites, 87.7% serve ETag headers on responses (70% good LCP, 1.9s median) and 12.3% serve responses without ETag headers (73% good LCP, 1.9s median).
React & Next.js 9,570 sites Next.js generates ETag headers by default (97.1% of React sites, 16 points higher LCP pass rate than sites without ETag).
Next.js enables generateEtags: true by default for pages. Across React sites, 97.1% serve ETag headers (85% good LCP, 1.4s median) compared with 2.9% that omit ETag headers (69% good LCP, 1.9s median).
By Arjen Karel · 210,902 crawled sites (196,263 with all devices Chrome field data, October 2026). How we measured.